Goodbye work!

I’m going back to school in August and I’m so excited. The problem is I need to have the difficult conversation with my boss. I know she’s going to ask “well why didn’t you tell me you’re going back to school” or “you’re working full time, this is going to be very hard to find people to cover your shifts”. I understand it’s never ideal for managers to lose full time employees.

I still want to work part time for the company to help pay for school, but I don’t think they will let me.

How do I go about this conversation in a respectful manner?